The present invention relates to a lancet device by which a lancet can be displaced along a piercing path to generate a piercing wound in a skin surface, in particular to obtain body fluid for diagnostic purposes, comprising a lancet drive, which has a drive for generating a drive force for a piercing movement of the lancet along the piercing path in the direction toward the skin surface, a retention means for generating a magnetic retention force for retaining the lancet in a tensioned position, and a trigger by which the retention force is reducible enough that the lancet is accelerated in the direction toward the skin surface under the effect of the drive force generated by the drive means.
Furthermore, the present invention relates to a method for operating a lancet device, by which a lancet is displaced along a piercing path to generate a piercing wound in a skin surface, in particular, to obtain body fluid for diagnostic purposes, comprising a lancet drive, by which a drive force is generated for a piercing movement of the lancet along the piercing path in the direction toward the skin surface by the lancet drive, a magnetic retention force is generated for retaining the lancet in a tensioned position by retention means, and the retention force is reduced enough by a triggering means that the lancet is accelerated in the direction toward the skin surface under the effect of the drive force generated by the lancet drive.
Lancet devices are required, for example, by diabetics, who have to check their blood sugar level frequently to be able to keep it within specific setpoint limits by insulin injections. Extensive scientific experimentation has proven that a dramatic reduction of the most severe long-term complications of diabetes mellitus (such as retinopathy with resulting blinding of the patient) may be achieved using an intensive treatment having at least four analyses per day.
For users of lancet devices, it is desirable on one hand to create the least amount of pain possible from piercing, and on the other hand to create the simplest possible operation and ability to handle the lancet device. These issues are of great significance.
A requirement for low-pain piercing is a piercing movement that is as rapid as possible and that has a short dwell time of the lancet in the skin. The use of drive springs has been proven in the prior art to produce a correspondingly strong acceleration of lancets. A disadvantage of lancet devices of this type is that manually tensioning the drive springs after completed piercing is cumbersome for many users. This is true in particular for people whose manual dexterity is restricted by age or illness.
A lancet device in which the drive spring is automatically tensioned by an electric motor offers increased user comfort in this regard, but has the disadvantage that it is larger and heavier due to the electric motor. A lancet device having an integrated electric motor therefore represents a burden for the user who must carry it around continuously for frequent measurements. In addition, production costs are significantly increased by an electric motor.
Furthermore, lancet devices are known in the prior art in which the drive force is generated electromagnetically using a coil. Lancet devices of this type are disclosed, for example, in WO 02/100460 A2 and U.S. Pat. No. 6,364,889. To cause a sufficiently rapid piercing movement for low-pain piercing using electromagnetic lancet drives of this type, strong magnetic fields must be generated. This requires relatively strong electric current flow through the drive coils used, which currents may be generated not at all or only with great effort in a small, compact, handheld device. Electromagnetic lancet drives have therefore been unable to thus far displace the use of mechanical drives having drive springs.
A lancet device having an electromagnetic drive which addresses these disadvantages is known from WO 2007/006399 A1, whose features are referred to herein in regard to advantageous features and designs of lancet drives. The publication relates, inter alia, to the fundamental principle of a piercing drive having a permanent magnet. The drive contains a permanent magnet and electromagnetic coils which allow a compensation of the permanent magnetic field and thus permit control of the drive unit for a piercing aid. The lancet is retained by magnetic forces in a first position and the lancet may no longer be retained in the position by compensation of the magnetic field in the event of corresponding powering of a coil, so that the lancet performs a piercing procedure driven by a spring. The lancet device known from this publication, which may also be referred to as a ballistic piercing aid, has a stop for delimiting the piercing depth, like other known embodiments of ballistic piercing aids. However, this embodiment has multiple consequences and disadvantages:                Noises arise upon triggering a piercing, e.g., loud clicking. These noises are often perceived as disturbing by users, or may startle the users, which may subjectively increase the sensation of pain from piercing.        Oscillations are excited in the lancet system, which are transmitted to the lancet stuck into the tissue and may thus cause or increase pain.        Because the stop is not perfectly inelastic, kinetic energy is transmitted from the stop back to the lancet, because of which the ballistic system comprising the lancet tends to reverberate along the axis of the piercing movement. This may even result in multiple lancet exits, which also cause pain.        
To suppress these undesirable accompanying effects, various complex auxiliary devices are required according to the prior art, which make the lancet device or the entire system larger and more expensive to manufacture.
If piercing or lancet devices of this type are to be integrated in a blood analysis unit, it is advisable to incorporate the actions of “tensioning” and “triggering” the lancet in the overall ergonomics, which succeeds especially well if they are operated automatically by the device, and/or may be started by the user using operating elements required in any case for an analysis device. In addition, electrical operating elements (switches, buttons, etc.) may then be placed more easily on ergonomically advisable points of the device exterior than mechanical operating elements to be grasped directly. The outlay for such a piercing device thus rises significantly.
Furthermore, path-controlled piercing aids are known (e.g., under the trade name Softclix®), which may be integrated relatively easily in automatic measuring systems and equipped with auxiliary functions. However, these path-controlled piercing aids always set internal masses into movement whose kinetic energy must ultimately be dissipated, which is performed using stops for functional and space purposes. These systems also cause significant noises.
Furthermore, electrical drives for piercing devices are known, e.g., from the above-mentioned WO 2002/100460. These are relatively quiet because they manage without final stops, but they have the disadvantage that all of the kinetic energy for the piercing, including the movement of the device masses which are required for the movement of the lancet, must be provided directly from the electrical power supply. Large inductances are required for generating the required forces which in turn require high voltages for a rapid current change. Thus, in addition to the energy supply (e.g., battery), a power supply (e.g., a capacitor) must also be housed in the device, which is designed for high voltages and provides the required amount of energy for a piercing procedure. Only approximately half of such an accumulator may be practically used, however. This power supply is thus as large as the energy supply itself in regard to the overall volume. This volume requirement makes it absolutely necessary to minimize the moved masses and the resistances and frictions on the piercing path, which requires additional outlay for the unpacking of piercing elements (lancets) from the sterile packaging. This is problematic because spare volume is not typically available in manually handled, mobile measuring systems for diabetics.